diff --git a/packages/core/LICENSE b/packages/core/LICENSE
new file mode 100644
index 0000000..4f9dbc7
--- /dev/null
+++ b/packages/core/LICENSE
@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2026 LUO YONG NENG
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/packages/core/README.md b/packages/core/README.md
new file mode 100644
index 0000000..0ae8cef
--- /dev/null
+++ b/packages/core/README.md
@@ -0,0 +1,72 @@
+# @zipkit/core
+
+台灣地址英譯與 3+3 郵遞區號查詢的核心邏輯，無框架依賴。
+
+此套件是 [Zipkit](https://github.com/ronload/zipkit) 的領域核心，提供 UPU 格式地址英譯、六碼郵遞區號（3+3）特異性比對，以及共用型別。純函式、無副作用，可用於任何 JavaScript / TypeScript 環境。
+
+ESM-only。以 [tsdown](https://tsdown.dev/) 建置，輸出 ESM 與型別宣告。
+
+## 安裝
+
+```bash
+pnpm add @zipkit/core
+```
+
+## API
+
+### `formatEnglishAddress(city, district, road, detail): string`
+
+將中文地址格式化為 UPU 標準英譯地址。輸出順序為 `[Room], [Floor], No. [Number], [Alley], [Lane], [Road], [District], [City] [Zip], Taiwan (R.O.C.)`。
+
+```ts
+import { formatEnglishAddress } from "@zipkit/core";
+
+formatEnglishAddress(
+  { name: "臺北市", en: "Taipei City", districts: [] },
+  { name: "中正區", en: "Zhongzheng Dist.", zip3: "100" },
+  { name: "忠孝東路一段", en: "Sec. 1, Zhongxiao E. Rd." },
+  { lane: "", alley: "", number: "5之1", floor: "3", room: "" },
+);
+// => "3F., No. 5-1, Sec. 1, Zhongxiao E. Rd., Zhongzheng Dist., Taipei City 100, Taiwan (R.O.C.)"
+```
+
+### `lookupZip6(ranges, roadName, lane, alley, number, numberSub, floor): string | null`
+
+以特異性評分比對地址與郵遞區號範圍規則，回傳六碼郵遞區號；無對應時回傳 `null`。條件越多（巷段、弄段、門牌範圍、單雙號、樓層）的規則優先採用。`ranges` 為該行政區的範圍規則陣列（由資料來源載入）。
+
+```ts
+import { lookupZip6 } from "@zipkit/core";
+
+// ranges: ZipRange[]（該行政區的範圍規則）
+const zip6 = lookupZip6(ranges, "忠孝東路一段", 0, 0, 5, 1, 3);
+// => "100002" 或 null
+```
+
+### `parseNumber(input): { number: number; sub: number }`
+
+解析含「之」記法的門牌號字串。
+
+```ts
+import { parseNumber } from "@zipkit/core";
+
+parseNumber("5之1"); // => { number: 5, sub: 1 }
+parseNumber("33"); // => { number: 33, sub: 0 }
+```
+
+## 型別
+
+匯出 `City`、`District`、`Road`、`ZipRange`、`AddressDetail` 五個領域型別，皆可作為 `import type` 引入。
+
+```ts
+import type {
+  City,
+  District,
+  Road,
+  ZipRange,
+  AddressDetail,
+} from "@zipkit/core";
+```
+
+## 授權
+
+[MIT](./LICENSE)
diff --git a/packages/core/package.json b/packages/core/package.json
index e1ff02b..d1186fd 100644
--- a/packages/core/package.json
+++ b/packages/core/package.json
@@ -1,8 +1,31 @@
 {
   "name": "@zipkit/core",
-  "version": "0.0.0",
+  "version": "0.1.0",
+  "description": "Framework-agnostic core for Taiwan address English (UPU) translation and 3+3 postal code lookup.",
+  "keywords": [
+    "taiwan",
+    "postal-code",
+    "zipcode",
+    "zip-code",
+    "address",
+    "upu",
+    "3+3",
+    "english-translation"
+  ],
+  "license": "MIT",
+  "author": "ronload",
+  "homepage": "https://github.com/ronload/zipkit/tree/main/packages/core#readme",
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/ronload/zipkit.git",
+    "directory": "packages/core"
+  },
+  "bugs": {
+    "url": "https://github.com/ronload/zipkit/issues"
+  },
   "private": true,
   "type": "module",
+  "sideEffects": false,
   "exports": {
     ".": {
       "types": "./dist/index.d.ts",
@@ -15,6 +38,9 @@
   "files": [
     "dist"
   ],
+  "publishConfig": {
+    "access": "public"
+  },
   "scripts": {
     "build": "tsdown",
     "dev": "tsdown --watch",